Solution : https://service.sap.com/sap/support/notes/844933 (SAP Service marketplace login required)
Key words :
'schedule line' tab title, distribute planned independent requirements, menu path edit -> distribution, 'table' tab title, edit -> period split, terms period split, existing distribution function, period split, planning table, distribution function
Related Notes :
| 64146 | Info on splitting in demand management/period split |